As shown in FIG. 1, the Taiwan Patent No. 82202299 discloses a ratchet wrench comprising a button 2 and a drive head 3. The drive head 3 has a connection rod 4 which is received within an insertion hole 5. The button 2 has a rack 1, which is engaged with the insertion hole 5 in which a corresponding rack is provided. When the button 2 is pressed, the rack 1 of the button 2 is disengaged with the insertion hole 5 so as to enable the drive head 3 to be bent to form a predetermined angle with the handle 6. As soon as the button 2 is relieved of the pressure exerting thereon, the button 2 is forced by the elastic force of a spring 7 to return to its original position. Such a prior art ratchet wrench as described above is defective in design in that the rack 1 of the button 2 is prone to displace and jam in the insertion hole 5. In order to prevent the jamming of the rack 1, it is necessary to turn the button 2 gently. The user of the prior art ratchet wrench is often annoyed by such inconvenience.
As shown in FIGS. 2 and 3, the Taiwan Patent Nos. 82210906 and 83206013 disclose respectively a ratchet wrench comprising a rod body 9 which is provided with a cam 8 for supporting an arresting member 10 so as to retain the drive head 11. The rod body 9 is not provided with a means for causing the rod body 9 to return to its original position automatically. As a result, the user of such prior art ratchet wrenches must keep turning the rod body 9 at the same time as when the prior art ratchet wrenches are at work. In addition, the contact area of the drive head 11 and the arresting member 10 is smooth and is vulnerable to deformation.
Now referring to FIG. 4, the Taiwan Patent No. 8221506 discloses a ratchet wrench, which comprises a drive head 12 having two lugs 13 and a steel ball 14 located between the two lugs 13. The steel ball 14 is intended to engage any one of the retaining slots 17 of the pivoting end 16 of the handle 15. One of the two lugs 13 of the drive head 12 is provided with a hole 18 for receiving a spring pull member 19 which has a protruded rod 20. The pivoting end 16 of the handle 15 is provided with a plurality of insertion holes 21. The protruded rod 20 is inserted into one of the insertion holes 21. In order to bend the drive head 12, it is necessary to pull the spring pull member 19 so as to cause the protruded rod 20 to disengage the insertion hole 21 of the handle 15. In the meantime, the steel ball 14 constantly supports any angle of any corresponding retaining slots 17 of the pivoting end 16 of the handle 15.
It is therefore readily apparent that the prior art ratchet wrenches are complicated in construction and are therefore not cost-effective. In addition, the prior art ratchet wrenches can not be used with ease and convenience.